title: Characteristic and functional analysis of toll-like receptors (TLRs) in the lophotrocozoan, Crassostrea gigas, reveals ancient origin of TLR-mediated innate immunity.
abstract: The evolution of TLR-mediated innate immunity is a fundamental question in immunology. Here, we report the characterization and functional analysis of four TLR members in the lophotrochozoans Crassostreagigas (CgTLRs). All CgTLRs bear a conserved domain organization and have a close relationship with TLRs in ancient non-vertebrate chordates. In HEK293 cells, every CgTLR could constitutively activate NF-κB responsive reporter, but none of the PAMPs tested could stimulate CgTLR-activated NF-κB induction. Subcellular localization showed that CgTLR members have similar and dual distribution on late endosomes and plasma membranes. Moreover, CgTLRs and CgMyD88 mRNA show a consistent response to multiple PAMP challenges in oyster hemocytes. As CgTLR-mediated NF-κB activation is dependent on CgMyD88, we designed a blocking peptide for CgTLR signaling that would inhibit CgTLR-CgMyD88 dependent NF-κB activation. This was used to demonstrate that a Vibrio parahaemolyticus infection-induced enhancement of degranulation and increase of cytokines TNF mRNA in hemocytes, could be inhibited by blocking CgTLR signaling. In summary, our study characterized the primitive TLRs in the lophotrocozoan C. gigas and demonstrated a fundamental role of TLR signaling in infection-induced hemocyte activation. This provides further evidence for an ancient origin of TLR-mediated innate immunity.
authors.affiliation: Key Laboratory of Marine Bio-resources Sustainable Utilization, Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xiaocui
authors.initials: X
authors.lastname: He
authors.forename: Feng
authors.initials: F
authors.lastname: Yu
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Xiang
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Karen L
authors.initials: KL
authors.lastname: Thorpe
authors.forename: Ziniu
authors.initials: Z
authors.lastname: Yu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015550:Cell Degranulation / Q000276:immunology; D002460:Cell Line; D049896:Crassostrea / Q000145:classification / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D015870:Gene Expression; D020869:Gene Expression Profiling; D017930:Genes, Reporter; D006434:Hemocytes / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D005810:Multigene Family; D053594:Myeloid Differentiation Factor 88 / Q000737:chemistry / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010802:Phylogeny; D011485:Protein Binding; D011487:Protein Conformation; D021381:Protein Transport; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D016207:Cytokines; D008024:Ligands; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D010455:Peptides; D051193:Toll-Like Receptors